Gas turbine exhaust diffuser having plasma actuator

ABSTRACT

A gas turbine is provided, including a turbine, an exhaust diffuser, and a plasma actuator. The turbine releases an exhaust gas. The exhaust diffuser receives the exhaust gas from the turbine. The exhaust diffuser has an inlet and an outlet, and at least one wall that is disposed between the inlet and the outlet. The plasma actuator produces a plasma along the at least one wall of the diffuser.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a gas turbine, and morespecifically to a gas turbine exhaust diffuser having a plasma actuatorfor producing a plasma.

Gas turbines generally include a compressor, a combustor, one or morefuel nozzles, a turbine and an exhaust diffuser. Air enters the gasturbine through an air intake and is compressed by the compressor. Thecompressed air is then mixed with fuel supplied by the fuel nozzles. Theair-fuel mixture is supplied to the combustors at a specified ratio forcombustion. The combustion generates pressurized exhaust gases, whichdrive blades of the turbine. An exhaust diffuser may be utilized toimprove efficiency of the last stage turbine blade, which is alsoreferred to as a last stage bucket, by decreasing the static pressure atthe turbine exit.

The exhaust diffuser generally consumes a large amount of space. Theexhaust diffuser includes an inlet and an outlet that are locatedbetween diverging walls of the exhaust diffuser. An axial length of theexhaust diffuser is measured between the inlet and the outlet of theexhaust diffuser. If the axial length of the diffuser is not sufficientand is too short, flow separation may occur at the diverging walls ofthe exhaust diffuser, which results in pressure losses.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a gas turbine is provided,including a turbine, an exhaust diffuser, and a plasma actuator. Theturbine releases an exhaust gas. The exhaust diffuser receives theexhaust gas from the turbine. The exhaust diffuser has an inlet and anoutlet, and at least one wall that is disposed between the inlet and theoutlet. The plasma actuator produces a plasma along the at least onewall of the diffuser.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a partially cross-sectioned schematic view of an exemplary gasturbine system having a compressor;

FIG. 2 is a cross-sectioned view of an exhaust diffuser shown in FIG. 1;

FIG. 3 is a cross-sectioned view of the exhaust diffuser shown in FIG. 2along section lines 3-3;

FIG. 4 is a cross-sectioned view of an exhaust strut shown in FIG. 2along section lines 4-4; and

FIG. 5 is an enlarged view of a plasma actuator as shown in FIGS. 2-4.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a schematic exemplary power generation systemindicated by reference number 10. The power generation system 10 is agas turbine system having a compressor 20, a combustor 22, a turbine 24,and an exhaust diffuser 26. Air enters the power generation system 10though an air intake 30 connected to the compressor 20, and iscompressed by the compressor 20. The compressed air is then mixed withfuel by a fuel nozzle 34 in a specific ratio for combustion. Thecombustion generates hot pressurized exhaust gas that drives blades (notshown) that are located within the turbine 24. The exhaust gas is sentfrom the turbine 24 to the exhaust diffuser 26.

FIG. 2 is an exemplary illustration of a side view of the exhaustdiffuser 26. The exhaust diffuser 26 includes an inlet 40, an outlet 42,an inner diffuser 44 and an outer diffuser 46. The inner diffuser 44includes an inner wall 48 and the outer diffuser 50 includes an outerwall 52. The inner wall 48 and the outer wall 52 are both locatedbetween the inlet 40 and the outlet 42. The inner wall 48 of the innerdiffuser 44 is generally concentric with the outer wall 52 of the outerdiffuser 46. Both the inner diffuser 44 and the outer diffuser 46 areoriented about an axis A-A. In the embodiment as shown, the outer wall52 of the outer diffuser 46 includes a generally divergingconfiguration. The inlet 40 of the exhaust diffuser 26 receives anexhaust gas 56 from the turbine 24 (shown in FIG. 1). A plasma generatoror actuator 60 is located on an outer surface 54 of the inner wall 48,and a plasma actuator 62 is located on an outer surface 58 of the outerwall 52. It should be noted that while FIG. 2 illustrates the plasmaactuator 60 on the inner wall 48 as well as the plasma actuator 62located on the outer wall 52, only one of the inner wall 48 or the outerwall 52 may include one of the plasma actuators 60 and 62 as well.

FIG. 3 is a sectional view of the exhaust diffuser 26 taken alongsection line 3-3. As seen in FIG. 3, both the inner wall 48 and theouter wall 52 include a 360° configuration. Specifically, referring nowto FIG. 2-3, the inner wall 48 of the inner diffuser 44 includes agenerally annular configuration, and the outer wall 52 of the outerdiffuser 46 includes a generally conical configuration. A series ofmanways 68 are located between the inner wall 48 and the outer wall 52.The manways 68 provide personnel access to the inner diffuser 44. In theembodiment as shown in FIG. 3, the manways 68 are each spaced at about a120° configuration apart from one another, however it is to beunderstood that the manways 68 may be arranged in a variety ofconfigurations as well. An outer surface 70 of each of the manways 68may include a plasma actuator 72 as well. The outer surface 70 of eachof the manways 68 are exposed to the exhaust gas 56 from the turbine 24(shown in FIG. 1).

Referring back to FIG. 2, an exhaust strut 80 is located within theexhaust diffuser 26 between the inner wall 48 and the outer wall 52. Theexhaust strut 80 includes a cross-section which is indicated by sectionline 4-4. Referring now to FIG. 4, which is an illustration of theexhaust strut 80 at section 4-4, the exhaust frame strut 80 includes across-section that is shaped as a cambered airfoil. The airfoil includesan upper camber portion 82 and a lower camber portion 84. The exhauststrut 80 has an outer surface 86, where a plasma actuator 88 may belocated on the upper camber portion 82 or the lower camber portion 84along the outer surface 86. It should be noted that while FIG. 4illustrates a cambered airfoil, it is to be understood that the airfoilmay include a generally symmetrical configuration as well.

FIG. 5 is an enlarged view of an exemplary plasma actuator 90, which maybe used along the inner wall 48, the outer wall 52, along the outersurface 70 of the manways 68, or on the outer surface 86 of the exhauststrut 80 (shown in FIG. 2). The plasma actuator 90 includes an innerelectrode 92, an outer electrode 94, and a dielectric material 96. Thedielectric material 96 is configured for conforming to a conical orgenerally curved surface. That is, the dielectric material 96 isconfigured for conforming to a non-planer surface. Therefore, the plasmaactuator 90 is configured for conforming to an outer surface of anobject that is conical or includes a generally curved profile. Forexample, referring now to FIG. 2, the plasma actuator 60 is disposedalong a generally annular outer surface 54, and the plasma actuator 62is disposed along a generally conical outer surface 58.

Referring back to FIG. 5, an AC power supply 100 is connected to boththe inner electrode 92 and the outer electrode 94. The AC power supply100 provides AC power to the inner electrode 92 and the outer electrode94. In one exemplary embodiment, the power consumption of the plasmaactuator 90 is 15 Watts per linear foot of plasma. When the amplitude ofthe AC voltage reaches a threshold value, the exhaust gas 56 from theturbine 24 (shown in FIG. 1) ionizes in a region of the largest electricpotential to form a plasma 102. The plasma 102 begins at an edge 104 ofthe outer electrode 94 and spreads over an area 106 projected by theouter electrode 94 that is adjacent the dielectric material 96. Theplasma 102 produces a force on the exhaust gas 56, which in turn causesa change in the pressure distribution along a curved surface 110. Thechange in pressure distribution generally reduces or substantiallyprevents flow separation when the plasma actuator 90 is energized by theAC power supply 100. Thus, in the embodiments as shown in FIGS. 2-5, theplasma actuator 90 improves efficiency of the last stage turbine blade(not shown) or last stage bucket of the turbine 24 (shown in FIG. 1) byincreasing the static pressure of the exhaust gas 56. The plasmaactuators as illustrated in FIGS. 2-5 provide a robust design that isrelatively simple, and also provides a relatively low amount of powerconsumption with real-time control.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A gas turbine, comprising: a turbine releasing an exhaust gas; anexhaust diffuser for receiving the exhaust gas from the turbine, theexhaust diffuser having an inlet, an outlet and at least one wall thatis disposed between the inlet and the outlet; and a plasma actuatorproducing a plasma along the at least one wall of the diffuser.
 2. Thegas turbine of claim 1, wherein the exhaust diffuser includes an innerdiffuser and an outer diffuser, wherein the inner diffuser is generallyconcentric with the outer diffuser.
 3. The gas turbine of claim 2,wherein the inner diffuser includes an inner wall, and wherein theplasma actuator is disposed along the inner wall of the inner diffuser.4. The gas turbine of claim 2, wherein the outer diffuser includes anouter wall, and wherein the plasma actuator is disposed along the outerwall of the inner diffuser.
 5. The gas turbine of claim 2, wherein theinner diffuser includes a generally annular configuration.
 6. The gasturbine of claim 2, wherein the outer diffuser includes a generallyconical configuration.
 7. The gas turbine of claim 2, comprising atleast one manway located between the inner diffuser and the outerdiffuser, wherein the at least one manway includes an outer manwaysurface, and wherein another plasma actuator is located along the outermanway surface.
 8. The gas turbine of claim 1, comprising an exhauststrut that is located between an inner wall and an outer wall of theexhaust diffuser, the exhaust strut having a cross-section, wherein thecross-section of the exhaust strut includes an airfoil shape.
 9. The gasturbine of claim 8, comprising an exhaust strut plasma actuator that isdisposed along an outer surface of the exhaust strut.
 10. The gasturbine of claim 1, wherein the plasma actuator includes an innerelectrode, an outer electrode, and a dielectric material.
 11. A gasturbine, comprising: a turbine releasing an exhaust gas; an exhaustdiffuser for receiving the exhaust gas from the turbine, the exhaustdiffuser having an inlet and an outlet, comprising: an inner diffuserdisposed between the inlet and the outlet, the inner diffuser having aninner wall; an outer diffuser disposed between the inlet and the outlet,the outer diffuser having an outer wall, the inner diffuser generallyconcentric with the outer diffuser; and a plasma actuator producing aplasma along at least one of the inner wall and the outer wall.
 12. Thegas turbine of claim 11, wherein the inner diffuser includes a generallyannular configuration.
 13. The gas turbine of claim 11, wherein theouter diffuser includes a generally conical configuration.
 14. The gasturbine of claim 11, comprising at least one manway located between theinner diffuser and the outer diffuser, wherein the at least one manwayincludes an outer manway surface, and wherein another plasma actuator islocated along the outer manway surface.
 15. The gas turbine of claim 11,comprising an exhaust strut that is located between an inner wall and anouter wall of the exhaust diffuser, the exhaust strut having across-section, wherein the cross-section of the exhaust strut includesan airfoil shape.
 16. The gas turbine of claim 15, comprising an exhauststrut plasma actuator that is disposed along an outer surface of theexhaust strut.